Image scanning apparatus, method of scanning images, and recording medium for realizing the method

ABSTRACT

An image scanning technique of the present invention shortens the time required for reading images of a plurality of originals set on an original tray. The positions of a lens  18  and a line of CCDs  20  are adjusted, so as to enable a scanning range of the line of CCDs  20  in a primary scanning direction to cover a plurality of originals. A first shooting range Z 1  of the line of CCDs  20  covers four trimming areas Tr 1 , Tr 2 , Tr 5 , and Tr 6 . The procedure of the image scanning technique first reads white reference data of a white reference plate in the first shooting range Z 1 , then scans the four trimming areas Tr 1 , Tr 2 , Tr 5 , and Tr 6  while fixing the shooting range to the first shooting range Z 1 , and carries out shading correction to correct image data obtained by the scan with the white reference data. This structure requires the process of scanning the white reference plate and updating the white reference data only once for correcting the image data of the plurality of originals.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a technique for scanning originals withan image sensor, such as CCDs (charge-coupled devices).

2. Description of the Related Art

An image scanning apparatus generally illuminates an original with lightand introduces light reflected from the original (or transmitted throughthe original) into a first-dimensional CCDs, in order to read imagesignals of the original from the first-dimensional CCDs. The respectiveelements of the first-dimensional CCDs do not have identical sensitivitycharacteristics. Even when light enters all the elements homogeneously,there is a scatter in the output level of the elements. Shadingcorrection is a typical procedure to correct the scatter in thesensitivity characteristics of the respective elements of theone-dimensional CCDs. The process of shading correction scans a whitereference plate (or a black reference plate) prior to the scan of theoriginal, and generates coefficient data used for correcting thesensitivities of the respective elements of the one-dimensional CCDs,based on the output signals with respect to the reference plate from theone-dimensional CCDs. The process of shading correction corrects theoutput signals of an image obtained by scanning the original with thecoefficient data.

It is here assumed that a plurality of originals are set on an originaltray. The plurality of originals have different scanning resolutions anddifferent widths. It is accordingly required to set a scanning angle ofthe one-dimensional CCDs for each original. The ‘scanning angle’ hererepresents an angle of a possible shooting range of thefirst-dimensional CCDs. The coefficient data used for correcting thesensitivities depend upon the scanning angle of the one-dimensionalCCDs. The prior art technique accordingly carries out the shadingcorrection for each of the plurality of originals set on the originaltray, prior to the scan of the original.

As mentioned above, the prior technique requires the shading correctionevery time when the target of the scan is moved to a next original amongthe plurality of originals set on the original tray. This means that theprocess of scanning the white reference plate and updating thecoefficient data used for correcting the sensitivities should be carriedout for each original. This undesirably lengthens the total timerequired for scanning images.

SUMMARY OF THE INVENTION

The object of the present invention is thus to shorten the total timerequired for scanning images of a plurality of originals set on anoriginal tray.

The above and the other related objects is realized by a first imagescanning apparatus for optically scanning images of a plurality oforiginals set on an original tray, the first image scanning apparatusincluding: a light source which illuminates each of the original; a lenswhich condenses light from the each of original to condensed light; anda liner image sensor, arranged at a position of concentration of thecondensed light, comprising a plurality of light-receiving elementsarrayed in a primary scanning direction for converting light toelectrical signals.

The first image scanning apparatus further includes:

a scanning range specifying unit which adjusts relative positions of thelens, the liner image sensor and the original tray so that a scanningrange of the linear image sensor in the primary scanning directionincludes at least two of the plurality of originals;

a color reference data generating unit which obtains an output signal ofthe linear image sensor for a preset color reference while the scanningrange of the linear image sensor is fixed to what has been specified bythe scanning range specifying unit, and generating color reference datafor correcting sensitivity of each light-receiving element of the linearimage sensor on the basis of the output signal;

a secondary scanning unit which moves the original tray relative to thelinear image sensor in a secondary scanning direction while the scanningrange of the linear image sensor is fixed to what has been specified bythe scanning range specifying unit; and

an electrical signal correction unit which corrects an electricalsignal, which is output from the linear image sensor as the originaltray is moving in the secondary scanning direction, with the colorreference data generated by the color reference data generating unit.

In the first image scanning apparatus of the present invention, thescanning range specifying unit adjusts the relative positions of theoptical lens, the linear image sensor and original tray, so that ascanning range of the linear image sensor in the primary scanningdirection includes at least two of the plurality of originals. While thescanning range of the linear image sensor is fixed to what has beenspecified by the scanning range specifying unit, the color referencedata is generated by the color reference data generating unit, and theimages of at least two originals are read by the linear image sensor asthe original tray is moving in the secondary scanning direction. Theelectrical signal correction unit corrects the electrical signals outputfrom the linear image sensor as the color reference data. Namely thesame color reference data generated by the color reference datagenerating unit can be applied to correct the electrical signalsrepresenting the images of at least two originals.

This structure effectively reduces the generating cycles of the colorreference data used for correcting the sensitivities of the linear imagesensor to be less than the number of the originals, thereby shorteningthe total time required for scanning the plurality of originals set onthe original tray.

In accordance with one preferable application, the secondary scanningunit successively scans at least two originals one by one in thesecondary scanning direction while the scanning range of the linearimage sensor is fixed to what has been specified by the scanning rangespecifying unit. In this application, the first image scanning apparatusfurther includes:

a data extraction unit which extracts image data of an originalcurrently being scanned by the secondary scanning unit from theelectrical signal corrected with the color reference data; and

a memory which stores the extracted image data.

In this preferable structure, the secondary scanning unit successivelyreads at least two originals one by one in the secondary scanningdirection. The required capacity of the memory accordingly correspondsto the image data of one original. This structure reduces the requiredcapacity of the memory for storing the image data.

In accordance with another preferable application, the first imagescanning apparatus further includes a pre-scan unit which scans a wholeimage representing all the plurality of originals set on the originaltray at a predetermined resolution. In this application, the scanningrange specifying unit includes:

a computation unit which specifies an angle of view of the linear imagesensor and a specific position of the linear image sensor in the primaryscanning direction to attain the scanning range, on the basis of thewhole image obtained by the pre-scan unit; and

an optical system shifting unit which adjusts the relative positions ofthe lens, the linear image sensor and the original tray in order toattain the angle of view and the specific position specified by thecomputation unit.

In the first image scanning apparatus of this structure, it ispreferable that the computation unit includes:

a trimming unit which specifies an effective range of each of theoriginal as a trimming area of each of the original, on the basis of thewhole image obtained by the pre-scan unit; and

a unit which calculates an angle of view and the specific position ofthe linear image sensor from the trimming area of each of the originalspecified by the trimming unit.

In the first image scanning apparatus of the above preferable structure,the secondary scanning unit successively scans the at least twooriginals one by one in the secondary scanning direction while thescanning range of the linear image sensor is fixed to what has beenspecified by the scanning range specifying unit. In this application,the first image scanning apparatus further includes:

a data extraction unit which extracts image data included in thetrimming area with respect to an original currently being scanned by thesecondary scanning unit from the electrical signal corrected with thecolor reference data; and

a memory which stores the extracted image data.

In accordance with one preferable structure, the trimming area is arectangular area specified by an operator with a pointing device.

In accordance with another preferable structure, the scanning rangespecifying unit further includes a memory which stores first datarepresenting the trimming area, second data representing the angle ofview specified by the computation unit, and third data representing thespecific position of the linear image sensor in the primary scanningdirection specified by the computation unit with respect to eachoriginal.

The present invention is also directed to a second image scanningapparatus for optically scanning images of at least one original set onan original tray, the second image scanning apparatus including: a lightsource which illuminates each of the original; a lens which condenseslight from each of the original to condensed light; and a linear imagesensor, arranged at a position of concentration of the condensed light,comprising a plurality of light-receiving elements arrayed in a primaryscanning direction for converting light to electrical signals.

The second image scanning apparatus further includes:

an original specification unit which specifies a resolution and aposition of each of the original set on the original tray;

a scanning range setting unit which sets a scanning range of the linearimage sensor in the primary scanning direction to a range that maximizesa number of originals included in the scanning range and enables each ofthe original to be scanned at a resolution of not lower than theresolution specified by the original specification unit, on the basis ofthe resolution and the position of each of the original;

an optical system shifting unit which adjusts relative positions of thelens, the linear image sensor and the original tray, in order to realizethe scanning range set by the scanning range setting unit; and

a secondary scanning unit which moves the original tray relative to theliner image sensor in a secondary scanning direction while the scanningrange of the linear image sensor is fixed to what has been realized bythe optical system shifting unit.

In the second image scanning apparatus of the present invention, theoriginal specification unit specifies a resolution and a position ofeach original set on the original tray. The scanning range of the linearimage sensor in the primary scanning direction depends upon theresolution and the position of the original. The scanning range of thelinear image sensor maximizes the number of originals included in thescanning range and enables each original to be scanned at a resolutionof not lower than the resolution specified by the original specificationunit. While the scanning range of the linear image sensor is fixed towhat has been realized by the optical system shifting unit, the imagesof the maximum number of originals included in the range are read by thelinear image sensor as the original tray is moving in the secondaryscanning direction. Namely this structure enables the maximum number oforiginals to be scanned without causing deterioration of the resolution,while the scanning range of the linear image sensor in the primaryscanning direction is fixed to what has been realized by the opticalsystem shifting unit.

This structure effectively reduces the number of driving the opticalsystem shifting unit to be less than the number of the originals,thereby shortening the total time required for scanning the plurality oforiginals set on the original tray.

The present invention is further directed to a first method of opticallyscanning images of a plurality of originals set on an original tray withan image scanning device, the image scanning device including: a lightsource which illuminates each of the original, a lens which condenseslight from each of the original to condensed light, and a linear imagesensor, arranged at a position of concentration of the condensed light,comprising a plurality of light-receiving elements arrayed in a primaryscanning direction for converting light to electrical signals.

The first method includes the steps of:

(a) adjusting relative positions of the lens, the linear image sensorand the original tray so that a scanning range of the linear imagesensor in the primary scanning direction includes at least two of theplurality of originals;

(b) obtaining an output signal of the linear image sensor for a presetcolor reference while the scanning range of the linear image sensor isfixed to what has been specified in the step (a), and generating colorreference data for correcting sensitivity of each light-receivingelement of the linear image sensor on the basis of the output signal;

(c) moving the original tray relative to the linear image sensor in asecondary scanning direction while the scanning range of the linearimage sensor is fixed to what has been specified in the step (a); and

(d) correcting an electrical signal, which is output from the linearimage sensor as the original tray is moving in the secondary scanningdirection, with the color reference data generated in the step (b).

Like the first image scanning apparatus discussed above, the firstmethod of the present invention requires the process of generating thecolor reference data only once for correcting the image data of at leasttwo originals. This structure effectively reduces the generating cyclesof the color reference data used for correcting the sensitivities of thelinear image sensor to be less than the number of the originals, therebyshortening the total time required for scanning the plurality oforiginals set on the original tray.

The present invention is also directed to a second method of opticallyscanning images of at least one original set on an original tray with animage scanning device, the image scanning device including: a lightsource which illuminates each of the original, a lens which condenseslight from each of the original to condensed light, and a linear imagesensor arranged at a position of concentration of the condensed lightcomprising a plurality of light-receiving elements arrayed in a primaryscanning direction for converting light to electrical signals.

The second method includes the steps of:

(a) specifying a resolution and a position of each of the original seton the original tray;

(b) setting a scanning range of the linear image sensor in the primaryscanning direction to a range that maximizes a number of originalsincluded in the scanning range and enables each of the original to bescanned at a resolution of not lower than the resolution specified inthe step (a), on the basis of the resolution and the position of each ofthe original;

(c) adjusting relative positions of the lens, the linear image sensorand the original tray, in order to realize the scanning range set in thestep (b); and

(d) moving the original tray relative to the linear image sensor in asecondary scanning direction while the scanning range of the linearimage sensor is fixed to what has been realized in the step (c).

Like the second image scanning apparatus discussed above, the structureof the second method effectively reduces the number of adjusting thepositions of the optical system to be less than the number of theoriginals, thereby shortening the total time required for scanning theplurality of originals set on the original tray.

The present invention also provides a first computer program product foroptically scanning images of a plurality of originals set on an originaltray with an image scanning device, the image scanning device including:a light source which illuminates each of the original, a lens whichcondenses light from each of the original to condensed light, and alinear image sensor, arranged at a position of concentration of thecondensed light, comprising a plurality of light-receiving elementsarrayed in a primary scanning direction for converting light toelectrical signals.

The first computer program product includes:

a computer-readable medium;

a first program code unit for causing a computer to adjust relativepositions of the lens, the linear image sensor and the original tray sothat a scanning range of the linear image sensor in the primary scanningdirection includes at least two of the plurality of originals;

a second program code unit for causing the computer to obtain an outputsignal of the linear image sensor for a preset color reference while thescanning range of the linear image sensor is fixed to what has beenspecified by the first program code unit, and to generate colorreference data for correcting sensitivity of each light-receivingelement of the linear image sensor on the basis of the output signal;

a third program code unit for causing the computer to move the originaltray relative to the linear image sensor in a secondary scanningdirection while the scanning range of the linear image sensor is fixedto what has been specified by the first program code unit; and

a fourth program code unit for causing the computer to correct anelectrical signal, which is output from the linear image sensor as theoriginal tray is moving in the secondary scanning direction, with thecolor reference data generated by the second program code unit,

wherein each of the program code units is recorded on thecomputer-readable medium.

Like the first image scanning apparatus and the first method discussedabove, the first computer program product carried out by the computereffectively reduces the generating cycles of the color reference dataused for correcting the sensitivities of the linear image sensor to beless than the number of the originals, thereby shortening the total timerequired for scanning the plurality of originals set on the originaltray.

The present invention is further directed to a second computer programproduct for optically scanning images of at least one original set on anoriginal tray with an image scanning device, the image scanning deviceincluding: a light source which illuminates each of the original, a lenswhich condenses light from each of the original to condensed light, anda linear image sensor arranged at a position of concentration of thecondensed light comprising a plurality of light-receiving elementsarrayed in a primary scanning direction for converting light toelectrical signals.

The second computer program product includes:

a computer-readable medium;

a first program code unit for causing a computer to specify a resolutionand a position of each the original set on the original tray;

a second program code unit for causing the computer to set a scanningrange of the linear image sensor in the primary scanning direction to arange that maximizes a number of originals included in the scanningrange and enables the each original to be scanned at a resolution of notlower than the resolution specified by the first program code unit, onthe basis of the resolution and the position of each of the original;

a third program code unit for causing the computer to adjust relativepositions of the optical lens, the linear image sensor and the originaltray, in order to realize the scanning range set by the second programcode unit; and

a fourth program code unit for causing the computer to move the originaltray relative to the linear image sensor in a secondary scanningdirection while the scanning range of the linear image sensor is fixedto what has been realized by the third program code unit,

wherein each of the program code units is recorded on thecomputer-readable medium.

Like the second image scanning apparatus and the second method discussedabove, the second computer program product carried out by the computereffectively reduces the number of adjusting the positions of the opticalsystem to be less than the number of the originals, thereby shorteningthe total time required for scanning the plurality of originals set onthe original tray.

These and other objects, features, aspects, and advantages of thepresent invention will become more apparent from the following detaileddescription of the preferred embodiments with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates internal structure of a flatbed scanner10 embodying the present invention;

FIG. 2 is a block diagram illustrating electrical structure of theflatbed scanner 10;

FIG. 3 is a flowchart showing an original image scanning routineexecuted by the CPU 30 of the flatbed scanner 10;

FIG. 4 illustrates an image of the original tray 12 after the trimmingspecification has been completed for all the originals P;

FIG. 5 shows the relationship between trimming areas Tr1 through Tr6 anda possible shooting range of a line of CCDs 20 in a primary scanningdirection ‘x’;

FIG. 6 shows structure of scan condition data DT representing scanningconditions; and

FIGS. 7(a)-(d) show an outline of the scanning process carried out inthe original image scanning routine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

One mode of carrying out the present invention is discussed below as apreferred embodiment.

FIG. 1 schematically illustrates internal structure of a flatbed scanner10 embodying the present invention. The flatbed scanner 10 includes anoriginal tray 12 horizontally moving in a y direction (referred toherein as a secondary scanning direction). A fluorescent lamp (lightsource) 14 is disposed below the horizontally-moving original tray 12 toextend in a direction perpendicular to the moving direction (an xdirection in FIG. 1 referred to herein as a primary scanning direction).Light emitted from the light source 14 reflects from originals P set onthe original tray 12 and impings on a line of CCDs (charge-coupleddevices) 20 with R, G, and B color filters via a mirror 16 and a lens 18to be converted to electrical signals. As the original tray 12 moves inthe secondary scanning direction ‘y’, the images of the originals P seton the original tray 12 are read as the electrical signals.

In the flatbed scanner 10, the lens 18 and the line of CCDs 20 aremovable in the y direction. Moving either one or both of the lens 18 andthe line of CCDs 20 in they direction regulates an angle of view θ thatis possibly shot in the line of CCDs 20 by the lens 18 (hereinafterreferred to as the scanning angle of the line of CCDs 20). By way ofexample, the scanning angle θ of the line of CCDs 20 is extended(widened) by moving the line of CCDs 20 toward of the lens 18 (that is,−y direction) while the lens 18 is fixed. Alternatively the scanningangle θ of the line of CCDs 20 is extended (widened) by moving the lens18 toward the line of CCDs 20 (that is, y direction) while the line ofCCDs 20 is fixed.

Both the lens 18 and the line of CCDs 20 are also movable in the xdirection. Integrally moving the lens 18 and the line of CCDs 20 in thedirection x without changing their positional relationship shifts thepossible shooting range of the originals P in the line of CCDs 20 in thex direction.

A white reference plate 22 is arranged on one end of the original tray12 (the first end in the moving direction) for generating whitereference data used in shading correction. The white reference plate 22is a board member having the surface homogeneously painted in white, andgives the white reference data as output signals of the line of CCDs 20corresponding to a white reference density of the white reference plate22.

FIG. 2 is a block diagram illustrating electrical structure of theflatbed scanner 10. The flatbed scanner 10 includes a CPU 30 and a busline 32 as well as the following components connected to the CPU 30 viathe bus line 32:

a main memory 34 for storing processing programs and working data (Theprocessing programs are executed by the CPU 30 to realize the functionsof a scanning range specifying unit 34 a, a color reference datagenerating unit 34 b, a secondary scanning unit 34 c, and an electricalsignal correction unit 34 d);

an auxiliary memory 36 for storing image data of scanned originals andother data used for the processing;

an A/D converter 38 for converting analog signals input from the line ofCCDs 20 to digital signals;

a mouse driver 40 for driving a mouse 41 functioning as a pointingdevice;

a keyboard controller 42 for outputting signals in response to operationof a keyboard 43;

a display controller 44 for controlling display of color images on acolor monitor 46;

a secondary scanning control unit 48 for outputting control signals toan original tray driving motor 49 that shifts the original tray 12 inthe secondary scanning direction ‘y’;

a lens shift control unit 50 for outputting control signals to anX-direction driving motor 51 and a Y-direction driving motor 52 thatrespectively shift the lens 18 in the x direction and in the ydirection; and

a CCD shift control unit 54 for outputting control signals to anX-direction driving motor 55 and a Y-direction driving motor 56 thatrespectively shift the line of CCDs 20 in the x direction and in the ydirection.

The original tray driving motor 49 is a stepping motor that is drivenand rotated in response to a pulse signal or control signal output fromthe secondary scanning control unit 48. The X-direction driving motor51, the Y-direction driving motor 52, the X-direction driving motor 55,and the Y-direction driving motor 56 are also stepping motors that aredriven and rotated in response to pulse signals or control signalsrespectively output from the lens shift control unit 50 and the CCDshift control unit 54.

The CPU 30 of the flatbed scanner 10 thus constructed executes anoriginal image scanning routine shown in the flowchart of FIG. 3.

When the program enters the routine of FIG. 3, the CPU 30 first carriesout a pre-scan process, which scans the whole original tray 12 at a lowresolution, at step S100. In the pre-scan process, while the secondaryscanning control unit 48 outputs a control signal to the original traydriving motor 49 to shift the original tray 12 in the secondary scanningdirection ‘y’, the CPU 30 inputs electrical signals representing theimage of the original tray 12 from the line of CCDs 20 via the A/Dconverter 38. The scanning angle θ of the line of CCDs 20 is set in arange that can shoot the entire whole width of the original tray 12 inthe primary scanning direction ‘x’. One scan of the line of CCDs 20 inthe secondary scanning direction ‘y’ enables input of the whole image ofthe original tray 12.

The CPU 30 initializes a variable ‘n’ (which variable counts) the numberof trimming areas (discussed later)) to zero at step S110. The CPU 30subsequently carries out trimming specification with respect to theimage of each original P set on the original tray 12 using the imagedata obtained by the pre-scan process at step S120. In the process oftrimming specification, the image data obtained by the pre-scan processare displayed on the color monitor 46. The operator specifies two pointson a diagonal in the image of the original P with the mouse 41 on thedisplay of the color monitor 46, and the CPU 30 stores a range definedby the specified two points as a trimming area.

The CPU30 then specifies a resolution with respect to the original P forwhich the trimming specification has been carried out, at step S121. Forexample, the operator may directly input a value representing theresolution from the keyboard 43. In another example the operator inputsa desired output size of the original P from the keyboard 43 and the CPU30 calculates the resolution from the desired output size and the sizeof the trimming area specified at step S120.

After the specification of the trimming area and the resolution has beenconcluded for an arbitrary original P on the original tray 12 at stepsS120 and S121 the variable ‘n’ is incremented by one at step S130. It isthen determined at step S140 whether or not the specification of thetrimming area and the resolution at steps S120 and S121 has beenconcluded for all the originals P. When it is determined at step S140that the specification has not yet been concluded for all the originalsP, the program returns to step S120 and repeats the specification forthe image of another original P. When it is determined at step S140 thatthe specification has been concluded for all the originals P, theprogram proceeds to step S150.

FIG. 4 illustrates an image of the original tray 12 after the trimmingspecification has been completed for all the originals P. In thisexample, six trimming areas Tr1 through Tr6 have been specifiedcorresponding to the number of the originals P.

At step S150 in the flowchart of FIG. 3, the CPU 30 obtains optimumscanning conditions for scanning the originals P, based on theinformation of the trimming areas and resolutions specified at step S120and S130. The scanning conditions define the sequence of scanning theoriginals P and the shooting range of the line of CCDs 20 in the primaryscanning direction ‘x’. The processing of step S150 determines theoptimum scanning conditions that enable each original P to be scanned ata preset scanning resolution and minimize the movements of the line ofCCDs 20 and the lens 18 in the primary scanning direction ‘x’.

FIG. 5 shows the relationship between the trimming areas Tr1 through Tr6and the possible shooting range of the line of CCDs 20 in the primaryscanning direction ‘x’. When the first through the sixth trimming areasTr1 through Tr6 are specified as illustrated in FIG. 5, the first, thesecond, the fifth, and the sixth trimming areas Tr1, Tr2, Tr5, and Tr6are within a first shooting range Z1 of the line of CCDs 20. Morespecifially, these four trimming areas Tr1, Tr2, Tr5, and Tr6 areincluded in the length of the first shooting range Z1 extendingrightward from the left-most end of the first trimming area Tr1 existingon the left-most position and are shot simultaneously. The third and thefourth trimming areas Tr3 and Tr4 are within a second shooting range Z2of the line of CCDs 20. The first shooting range Z1 and the secondshooting range Z2 are set when the position of the lens 18 and the lineof CCDs 20 is adjusted to enable the originals in the shooting ranges Z1and Z2 to be scanned at the maximum scanning resolution specified forthe respective originals. The higher scanning resolution generallynarrows the shooting range. The first and the second shooting ranges Z1and Z2 are accordingly the narrowest shooting ranges for scanning thetrimming areas Tr1, Tr2, Tr5, and Tr6 in the range Z1 and the trimmingareas Tr3 and Tr4 in the range Z2.

Referring back to the flowchart of FIG. 3, at step S150, the CPU 30 setsthe first shooting range Z1 for scanning the first, the second, thefifth, and the sixth trimming areas Tr1, Tr2, Tr5, and Tr6 and thesecond shooting range Z2 for scanning the third and the fourth trimmingareas Tr3 and Tr4. The CPU 30 further specifies the sequence of scanningthe images of the trimming areas in the respective shooting ranges Z1and Z2. In accordance with a concrete example, the CPU 30 specifies ascanning sequence as the first, the second, the fifth, and the sixthtrimming areas Tr1, Tr2, Tr5, and Tr6 in the first shooting range Z1 anda scanning sequence as the third and the fourth trimming areas Tr3 andTr4 in the second shooting range Z2. Namely the specified order ofscanning images goes as the first, the second, the fifth, the sixth, thethird, and the fourth trimming areas Tr1, Tr2, Tr5, Tr6, Tr3, and Tr4.

These preset scanning conditions are stored in a data structure givenbelow in the main memory 34. FIG. 6 shows structure of scan conditiondata DT representing the scanning conditions. The scan condition data DTincludes the following data items Da through Dd prepared for eachoriginal:

(1) data item Da representing the trimming areas Tr1 through Tr6corresponding to the respective originals;

(2) data item Db representing a preferential number allocated to eachoriginal to define the scanning sequence;

(3) data item Dc representing the scanning angle θ of the line of CCDs20; and

(4) data item Dd representing the position of the line of CCDs 20 andthe lens 18 in the primary scanning direction ‘x’ when each original isscanned.

The value of the data item Dd defines the position of a given part (forexample, an end) of the line of CCDs 20 and the lens 18 as adisplacement from a fixed position. The data items Dc and Dd determinethe possible shooting range of the line of CCDs 20 in the primaryscanning direction ‘x’.

Referring back again to the flowchart of FIG. 3, after specifying theoptimum scanning conditions for each original, at step S150, the CPU 30sets a variable ‘i’ equal to one at step S160. At subsequent step S170,the CPU 30 reads the data items Da, Dc, and Dd with respect to anoriginal having the data item Db equal to the preset variable ‘i’, thatis, an i-th original, to which a preferential number ‘i’ has beenallocated, using the data item Db of the scan condition data DTspecified at step S150 as a retrieval key. It is then determined at stepS180 whether or not the current values of the data items Dc and Dd aredifferent from the previous values subjected to the determination in theprevious cycle of this step, that is, whether or not there is any changein the shooting range of the line of CCDs 20.

When it is determined at step S180 that at least either one of thecurrent values of the data items Dc and Dd has been changed, that is,there is any change in the shooting range of the line of CCDs 20, theCPU 30 changes the shooting range of the line of CCDs 20 in the primaryscanning direction ‘x’ at step S190. In accordance with a concreteexample, the CPU 30 determines control amounts of the lens 18 and theline of CCDs 20 required for realizing the angle of view θ defined bythe data item Dc read at step S170 (either one of the control amountsmay be equal to zero) and outputs control signals representing therequired control amounts to the lens shift control unit 50 and the CCDshift control unit 54, so as to shift either one or both of the lens 18and the line of CCDs 20 by predetermined distances in the secondaryscanning direction ‘y’ This process adjusts the scanning angle θ of theline of CCDs 20 to the value defined by the data item Dc. The CPU 30also outputs control signals representing control amounts based on thedata item Dd read at step S170 to the lens shift control unit 50 and theCCD shift control unit 54, so as to shift the lens 18 and the line ofCCDs 20 in the primary scanning direction ‘x’ by predetermined distancescorresponding to the value of the data item Dd. This process moves theshooting range of the line of CCDs 20 in the primary scanning direction‘x’ by a desired amount.

At step S190, the CPU 30 specifies the scanning angle θ of the line ofCCDs 20 and the position in the primary scanning direction ‘x’ of theshooting range defined by the scanning angle θ. This procedure changesthe possible shooting range of the line of CCDs 20 in the primaryscanning direction ‘x’ to a desired position.

The program then proceeds to step S200 to read the image of the whitereference plate 22. In accordance with a concrete procedure, in responseto a predetermined control signal output from the secondary scanningcontrol unit 48 to the original tray driving motor 49, the shootingposition of the line of CCDs 20 is shifted to the position of the whitereference plate 22. The CPU 30 receives electrical signals representingthe image of the white reference plate 22 input from the line of CCDs 20via the A/D converter 38. The shooting range of the line of CCDs 20 inthe primary scanning direction ‘x’ at this moment is fixed to thedesired shooting range specified at step S190. The input image of thewhite reference plate 22 is stored as white reference data into the mainmemory 34.

The CPU 30 subsequently goes to step S210. When it is determined at stepS180 that neither of the data items Dc and Dd has been changed, that is,there is no change in the shooting range of the line of CCDs 20, theprogram skips the processing of steps S190 and S200 and proceeds to stepS210. At step S210, the CPU 30 scans the trimming area defined by thedata item Da read at step S170. In accordance with an examplary, thesecondary scanning control unit 48 outputs a control signalcorresponding to the trimming area defined by the data item Da to theoriginal tray driving motor 49, and the line of CCDs 20 scans the rangein the secondary scanning direction ‘y’ specified by the trimming area.The CPU 30 accordingly receives electrical signals representing theimage of the trimming area input from the line of CCDs 20 via the A/Dconverter 38.

At step S210, the CPU 30 also carries out shading correction of theimage data input from the line of CCDs 20. The shading correctioncalculates a scatter in the respective elements of the line of CCDs 20and equalizes the outputs of the respective elements. The image datataken by the line of CCDs 20 are corrected with the white reference datastored in the main memory 34 at step S200. The shading correction is aknown technique to the skilled in the art and is thus not specificallydescribed here. The shading correction corrects the image data taken bythe line of CCDs 20 by each one line in the primary scanning direction.

At step S210, the CPU 30 further extracts a part corresponding to thetrimming area, that is a part of the range in the primary scanningdirection ‘x’ defined by the trimming area in question, from the imagedata of one line in the primary scanning direction ‘x’ after the shadingcorrection, and stores the extracted data part into the main memory 34.

FIG. 7 shows an outline of the processing carried out at step S210. Theprocessing first moves the shooting range of the line of CCDs 20 to adesired position in the secondary scanning direction ‘y’ as shown inFIG. 7(a). In this state, the shooting range of the line of CCDs 20 inthe primary scanning direction ‘x’ includes the plurality of trimmingareas Tr1 and Tr2 as clearly understood from FIG. 7(a). The processingthen takes image data of one line in the primary scanning direction ‘x’at the desired position in the secondary scanning direction ‘y’ as shownin FIG. 7(b) and stores the image data of one line into the main memory34. The processing subsequently carries out shading correction for theimage data of one line shown in FIG. 7(c), extracts a part correspondingto the i-th trimming area from the image data of one line in the primaryscanning direction ‘x’ after the shading correction as shown in FIG.7(d), and stores the extracted data part into the main memory 34.

The shooting range of the line of CCDs 20 is then shifted by one line inthe secondary scanning direction ‘y’, and the processing of FIGS. 7(a)through 7(d) is repeated for the new line. This processing is repeateduntil the shooting range of the line of CCDs 20 exceeds the trimmingarea in the secondary scanning direction ‘y’. This enables image datarepresenting an image in the trimming area having the i-th preferentialnumber to be stored into the main memory 34.

Referring back to the flowchart of FIG. 3, the CPU 30 increments thevariable ‘i’ by one at step S220 and determines at step S230 whether ornot the variable ‘i’ is greater than the variable ‘n’ set at step S130.When the variable ‘i’ is not greater than the variable ‘n’, the programreturns to step S170 and repeats the processing of steps S170 throughS210 for a next trimming area having a next preferential number. When itis determined at step S230 that the variable ‘i’ is greater than thevariable ‘n’, the program goes to END and exits from this routine.

This original image scanning process is applied to scan a plurality oforiginals P set on the original tray 12 in the following manner. Asdescribed previously, the original image scanning process specifies, forexample, the six trimming areas Tr1 through Tr6 shown in FIG. 4. Theconcrete procedure of the image scanning process is discussed below inan example of the six trimming areas Tr1 through Tr6 thus specified. Theprocess first reads the white reference data representing the image ofthe white reference plate 22 taken in the first shooting range Z1 shownin FIG. 5 by the line of CCDs 20. The process then reads an image in thefirst trimming area Tr1 taken in the first shooting range Z1 by the lineof CCDs 20. The process subsequently reads an image in the secondtrimming area Tr2 while not changing the shooting range of the line ofCCDs 20 in the primary scanning direction ‘x’, that is, fixing theshooting range to the first shooting range Z1. The process then readsimages in the fifth trimming area Tr5 and in the sixth trimming area Tr6while fixing the shooting range to the first shooting range Z1.

The shooting range of the line of CCDs 20 in the primary scanningdirection ‘x’ is then changed to the second shooting range Z2 shown inFIG. 5. The process first reads the white reference data representingthe image of the white reference plate 22 taken in the second shootingrange Z2, subsequently reads an image in the third trimming area Tr3taken in the second shooting range Z2, and then reads an image in thefourth trimming area Tr4 while fixing the shooting range to the secondshooting range Z2.

In the flatbed scanner 10 of the embodiment, the process of scanning thewhite reference plate 22 and updating the white reference data isrequired only once for correcting the image data of the four originalsin the first, the second, the fifth, and the sixth trimming areas Tr1,Tr2, Tr5, and Tr6. Similarly the same process is required only once forcorrecting the image data of the two originals in the third and thefourth trimming areas Tr3 and Tr4. Namely the process of scanning thewhite reference plate 22 and updating the white reference data isrequired only once for correcting the image data of two or moreoriginals. This effectively reduces the generating cycles of the whitereference data used for correcting the sensitivities of the line of CCDs20 to be less than the number of the originals P, thereby shortening thetotal time required for scanning the images of the plurality oforiginals P set on the original tray 12.

The flatbed scanner 10 of the embodiment does not simultaneously scan aplurality of originals included in one shooting range of the line ofCCDs 20 in the primary scanning direction, for example, four originalsspecified by the first, the second, the fifth, and the sixth trimmingareas Tr1, Tr2, Tr5,and Tr6, but individually scans each of theoriginals. The required capacity of the main memory 34 for storing theimage data thus corresponds to the size of the image data of the largestoriginal. This favorably saves the memory resource.

The structure of the embodiment individually scans each of a pluralityof originals in the secondary scanning direction. One modifiedstructure, however, simultaneously scans a plurality of originals in thesecondary scanning direction. This modified structure requires a greatercapacity of the memory for storing image data, but shortens the totaltime required for scanning the images.

In the structure of the embodiment, the color reference data generatingunit 34 b generates the white reference data from the white referenceplate 22. Another possible structure generates black reference data froma black reference plate and carries out shading correction with theblack reference data. Still another possible structure carries outshading correction with both the white reference data and the blackreference data.

The structure of the embodiment reads image signals representing theoriginals P set on the original tray 12 from the line of CCDs 20, whichreceives the light emitted from the light source 14 and reflected fromthe originals P set on the original tray 12. One modified structurereads image signals from the line of CCDs 20, which receives the lighttransmitted through the originals P.

In the above embodiment, both the first and the second shooting rangesZ1 and Z2 include a plurality of originals. As the result of thespecification of the optimum scanning conditions at step S150, however,either one of the first and the second shooting ranges Z1 and Z2 mayinclude a plurality of originals, while the other may include only oneoriginal.

The present invention is not restricted to the above embodiment, butthere may be many modifications, changes, and alterations withoutdeparting from the scope or spirit of the main characteristics of thepresent invention.

It should be clearly understood that the above embodiment is onlyillustrative and not restrictive in any sense. The scope and spirit ofthe present invention are limited only by the terms of the appendedclaims.

What is claimed is:
 1. An image scanning apparatus for opticallyscanning images of a plurality of originals set on an original tray,said image scanning apparatus comprising: a light source whichilluminates each said original; a lens which condenses light from saideach original to condensed light; a linear image sensor, arranged at aposition of concentration of said condensed light, said linear imagesensor comprising a plurality of light-receiving elements arrayed in aprimary scanning direction for converting light to electrical signals; ascanning range setting unit which sets a plurality of scanning ranges ofsaid linear image sensor in said primary scanning direction, each ofsaid scanning ranges including at least one of said plurality oforiginals, at least one of said scanning ranges including at least twoof said plurality of originals; an optical system shifting unit whichadjusts relative positions of said lens, said linear image sensor andsaid original tray in order to sequentially realize said plurality ofscanning ranges set by said scanning range setting unit; a colorreference data generating unit which obtains, for each said scanningrange, an output signal of said linear image sensor for a preset colorreference and which generates respective color reference data for eachsaid scanning range for correcting sensitivity of each light-receivingelement of said linear image sensor on the basis of said output signal;a secondary scanning unit which moves said original tray relative tosaid linear image sensor in a secondary scanning direction while thescanning range of said linear image sensor is fixed; and an electricalsignal correction unit which corrects an electrical signal which isoutput from said linear image sensor while said original tray is movingin said secondary scanning direction, as a function of said colorreference data.
 2. An image scanning apparatus in accordance with claim1, wherein said secondary scanning unit successively scans said at leasttwo originals located side by side in the secondary scanning directionwhile the scanning range of said linear image sensor is fixed, saidimage scanning apparatus further comprising: a data extraction unitwhich extracts image data of one of said two side by side originalsbeing scanned by said secondary scanning unit from said electricalsignal corrected with said color reference data; and a memory whichstores said extracted image data.
 3. An image scanning apparatus inaccordance with claim 1, further comprising: a pre-scan unit which scansan image area encompassing all said plurality of originals set on saidoriginal tray at a predetermined resolution, wherein said scanning rangesetting unit specifies an angle of view of said linear image sensor anda specific position of said linear image sensor in the primary scanningdirection for each of said scanning ranges to attain said scanningrange, on the basis of data obtained by said pre-scan unit; and whereinsaid optical system shifting unit adjusts said relative positions ofsaid lens, said linear image sensor and said original try in order toattain said angle of view and said specific position specified by saidsetting unit.
 4. An image scanning apparatus in accordance with claim 3,wherein said setting unit comprises: a trimming unit which specifies aneffective range of each said original as a function of a trimming areaof said each original, on the basis of information concerning said imagearea obtained by said pre-scan unit; and a unit which calculates saidangle of view and said specific position of said linear image sensorfrom said trimming area of said each original specified by said trimmingunit.
 5. An image scanning apparatus in accordance with claim 4, whereinsaid secondary scanning unit sequentially scans at least two originalsin said secondary scanning direction while scanning range of said linearimage sensor is fixed and while said original tray is stationaryrelative to said linear image sensor, said image scanning apparatusfurther comprising: a data extraction unit which extracts image data ofsaid trimming area of one of said at least two originals being scannedby said secondary scanning unit from said electrical signal correctedwith said color reference data; and a memory which stores said extractedimage data.
 6. An image scanning apparatus in accordance with claim 4,wherein said trimming area is a rectangular area specified by anoperator with a pointing device.
 7. An image scanning apparatus inaccordance with claim 4, wherein said scanning range specifying unitfurther comprises: a memory which stores, for each original, first datarepresenting said trimming area, second data representing said angle ofview, and third data representing said specific position of said linearimage sensor in the primary scanning direction.